Electrical discharge tube



Aug. W, 1948. J;.S. HICKEY ET AL ELECTRICAL DISCHARGE TUBE 2 Sheets-Sheet 1 Filed Sept. 24, 1946 W E m m W v 2A nnm w hm M/e w f WAVJ V 1948- J. s. HICKEY ET AL 2,446,765

ELECTRICAL DISCHARGE TUBE Filed Sept. 24, 1946 2 Sheets-Sheet 2 CA PA CITY MEHSURl/VG INSTR Inventors:

John S. Hickey, William H. Teare,

ELECTRICAL DISCHARGE TUBE York Application September 24, 1946, Serial No. 699,002

6 Claims.

This invention relates to electrical discharge devices such as those of the grid controlled discharge type has as its obi ect the provision of an improved construction having numerous advantages such as simplicity for quantity manufacturing purposes. the possibility of precision ssembiy of its various parts by relatively inexperienced workers, relatively close spacing of the various electrodes without danger of disturbance of their relative positions bv warping during use and improved relative high power output resultin from a novel shaping of the electrodes hereinafter to be described.

The features of the invention desired to be protected are set forth in the appended claims. The invention itself together with further objects and advantages thereof will best be understood from the following description taken in connection with the accompanying drawings in which Fig. 1 represents a cross-sectional View of a grid controlled discharge device embodying the invention; Fig. 2 represents the plan view of the grid electrode of Fig. 1; Fig. 3 represents an elevational view of a jig for assembling the grid and anode of Fig. 1 in accurately spaced relation; while Fig. 4 represents an elevational View partly in cross-section of a fixture for positioning the cathode within its assembly. Like numerals have been employed to designate like parts throughout the drawings.

Referring now to Fig. 1 the discharge device there shown comprises an annular anode i, a grid 2, and a cathode 3, all of which are included within an hermetically sealed envelope c. The envelope it includes a cylindrical metallic member 5 having an inwardy protruding flange portion 6, a cylindrical insulatin member i preferably of glass. an annular metallic member 8 affixed to the member l, a cylindrical metallic member 9 having e Jwardly extending peripheral flange portior and a cylindrical metallic member it havin an outwardly extending flat annular flange portion l 2 terminated by a longitudinal flange portion 83. The glass member 1' may be hermetically afiixed to the flange portion of member 5 and the annular member 8 while the portion ii of member 8 may be hermetically afflxed to the member The flange portion is of member H may be similarly affixed to the member To close the upper end of the envelope and to support anode i there is provided a metallic closure member it having an outwardly extending flange portion i5, a cylindrical portion i i, a frustoconical portion ll terminating in an inwardly extending flange portion 18, all

of these portions preferably being integral with each other that is, stamped in one piece. The member M may be hermetically sealed to the flange portion 6 of member 5. A tubular member l9 hermetically sealed through a central oriflce in member I i ma be provided for the purpose of evacuating the envelope in the manner well known in the art and to complete the process it may be compressed as indicated'at 20 to form a hermetic seal. The lower end of the envelope may be sealed by means of the glass ring 2! hermetically sealed between the member l l and a cylindrical metallic cathode supporting member 22; a similar glass head 23 being provided for the purpose of hermetically sealing the cathode supporting member 22. All of theglass to metal junctures indicated may of course be hermetically sealed by any of the suitable glass to metal sealing methods known in the art. While the metal to metal junctures may be similarly sealed by suitable processes such as brazing, welding or equivalent methods.

The cathode 3 may be constructed as follows. The cathode supporting member 22 may be provided with a collar 24 having longitudinally extending flange portions 25 and 25, the flange portion 26 being secured to the cathode supporting cylinder 22 by welding or other means. In order to minimize heat conduction between the cylinder 22 and the heated cathode portion presently to be described there may be afiixed to flange portion 25 a cylinder 2? of relatively thin material preferably metallic and of low heat conductivity. It will be understood that the thinness of the cylinder will in itself inhibit the flow of heat longitudinally of its wall. An annular member 23 may be afiixed to the cylinder 21 by means of its longitudinally extending flange 29 welded or brazed to cylinder 2? at a point substantially separated from the flange 25. On the upper end of cylinder 21 there may be welded an annular shaped cathode surface 38 having a longitudinally extending flange 3i protruding toward the member 23 in such a manner as to form an annular chamber defined by the cylinder 21, the cathode surface 3d, the flange 3i and the member 28. The cathode surface so may be coated on its upper space with any of the suitable thermionically emissive coatings well known in the For the purpose of heating the surface 30 to the temperature of thermionic emission there is provided a flat spiral heater coil 32 positioned adjacent to the lower surface of the oathode surface 353. The coil 32 may be insulated by any suitable means such as a coatin of alumina and may have its outer end conductively connected to the cylinder 2! and its inner end to lead 33 extending to the terminal 34 which passes through the glass bead to 23 to form an externally accessible terminal for the coil. The cathode supporting member 22 may form an externally accessible terminal for the other end of the spiral coil through the conductive path formed by the cylinder 21, collar 24, and member 22. A wire screen 35 may be provided over the inner surface of the flange 3| in order to maintain uniform potential distribution throughout this area of the cathode. Between the spiral heater 32 and the member 28 there may be provided a series of laminations 36 of wrinkled metallic foil which serves to reflect the heat from the heater spiral upward to the cathode surface thereby improving the thermal efficiency of the cathode.

In a manner well known in the art a suitable getter for absorbing residual gases from the envelope during the evacuation process may be provided in the form of a spiral coil 31 of suitable getter material. The coil 31 is shown as being connected at one end to a lead 38 and may be connected in its opposite end to the collar 24 as indicated at 39. As is well understood in the art the metallic material of the coil 3! may be flashed at the end of the evacuation process by the imposition of a suitable electric potential between the lead 38 and the cathode supporting member 22 thereby causing a sufficient electric current passing through the spiral to vaporize its substance.

The anode I may comprise any suitable annular construction having a surface conforming to the shape of its supporting member i4 and being afiixed thereto as by welding or brazing. As shown the anode may include an annular raised portion 40 which presents to the cathode and the grid a substantially annular active surface of similar shape to the active surfaces of the cathode and the grid. The anode may be formed of any suitable material such as copper or iron coated with copper.

The structure of grid 2 is shown in greater detail in Fig. 2. It comprises a fiat annular portion 4| having a diametrical rib 42 and a plurality of grid wires 43 which are stretched across the lower surfaces of the portions 4| and 42 in parallel configuration preferably perpendicular to the rib 42. They may be aflixed both to rib 42 and portion 4| by any suitable method such as brazing or welding. Because of the added support for the grid wires furn shed by rib 42 this construction has been found to permit the use of extremely fine grid wires closely positioned with respect to each other. That is to say the relatively short length of that portion of wires suspended between supports reduces the danger of their warping under their own weight or from thermal effects. The portions 42 and 4| will be found to afford sufiic ent support to the fine grid wires to maintain them in their relatively close positions to each other for a substantial tube life. It will be noted that the construction also provides a substantially annular shaped active grid surface presented to the corresponding annular surfaces of the cathode and anode.

The annular configuration of the active surfaces of the cathode, the anode and the grid has the advantage that a maximum active surface area for the electrodes may be obtained with a minimum length of the unsupported portion of the grid wires e. g., the portion hanging between the rib 42 and annular portion 4|. As already indicated, minimizing this length results in a more durable structure less susceptible to warping of the fine grid Wires. By way of comparison it is noted that if the active surfaces of the electrodes were, for example, in the configuration of a circle having an active area equal to that of the aforesaid annular configuration, then the length of the unsupported portion of the grid Wires across the circle diameter would be substantially greater thereby increasing the danger of distortion by warping caused by thermal expansion or stretching due to the weight of the wires. Moreover, it will be found that a more efficient ratio of heat dissipation to power output of the tube may be obtained by virtue of this annular configuration of the electrodes, thereby facilitating cooling of the device.

In the manufacturing process, the aforedescribed device may be assembled most conveniently in a series of operations in which the entire tube structure is assembled in three separate unitary structures as follows: The elements comprising the member 9, member 8, member 1, member 5 and member l4 together with the anode are assembled as a unitary anode structure. As a second unit, there may be assembled a grid structure comprising the grid 2 and a metallic grid supporting cylinder 44 to which the grid 2 is conductively aifixed as by welding or other suitable means, the side having the grid wires 43 preferably facing toward the cathode 3 as shown. Cylinder 44 may be provided with an inwardly directed annular flange 45 to facilitate attachment of the grid. A third unitary structure, the cathode 3 together with its supporting cylinder 22, bead 23, terminal 34 and lead 38 may be assembled in the cylinder H by means of the ring 2|. A fixture for effecting the assembly of this cathode structure will be described hereinafter in conjunction with Fig. 4.

The first step of the final assembly may begin with the assembly of the anode and grid unitary structures by means of the jig shown in Fig. 3. In'this figure the anode unit is affixed to an arm 46 of a clamp or vise like structure having a base 41 and a second arm 48. Arm 46 may have a central opening to accommodate the member IS. The grid structure and in particular the grid cylinder 44 are next slid into the member 9 and placed firmly therein by means of a head 49 adjustably attached to an arm 48 by means of the screw member having threads engaging with corresponding threads in a threaded aperture in arm 48. The motion of the head 49 to push the grid structure into member 9 may be accomplished by operation of a thumb screw 5|. Thus the inner peripheral surface of a longitudinal portion of member 9 adjacent its open end is slid over and engages the outer peripheral surface of a longitudinal portion of the grid end of cylinder 44.

By means of the thumb screw 5| the grid may be positioned in any desired distance relation with respect to the anode. For the purpose of determining when the proper spatial relation between the anode I and grid 2 has been reached there may be provided a means for measuring the capacity between the grid and anode, the motion of the grid being stopped when such capacity measuring means indicates that the capacity between the anode and grid has reached that correspondin to the desired spatial separation. Such a means may be of any of the types well known in the art such as a capacitance bridge indicated zgeeegrer schematically by the bloclri'zl and connected to the respective anode and cathod structures by any suitable leads sucli-ascontacts 53 and-54 which maybe in spring contact with" members a and" 9 respectively. It will be -understoodthat when-the gridhas bee'n'properly spaced-the cylin derM and member 9willbe permanently affixed to each other'to prevent relativemoticn. Such affixing may be 'accomplisliedby welding or any other"suit'ablemeansi Precisepositionin'g ofithe grid ZWith'respect to the cathode 3' mayjbe' accomplished in thefoll'owing manner: Itwill be notedthat the-supporting cylinder lfiifor'theg'rid 2""extendsbeyond' the end of the membersfand'that thereby it may be employedto'po'sitionboththe anode and grid structures 2 with respect to thevcathode 3 by affixing cylinder M on the flange portion I2 of member H; To'this' endth'e length-oi the'cylinder' t i is accurately finished prior to final assembly and the flat inner surface of annular flangeportion I2 is accurately finished so that when the grid and cathodestructures are assembled with the lower end of cylinder 44 resting on=the'*flange IZ the anode and grid will be preciselypositioned with respect thereto and withrespect to the cathode. After'the foregoing, the-'combined anode and grid structures may be assembled to the cathode structure simply by positioning the cylinder 44 within the flange portion l3 and thereafter hermetically sealing the flange E3 to the member 9 as by welding.

In order to provide for precise positioning of the cathode 3 with respect to the flange portion l2, the cathode structure comprising the aforedescribed elements may be assembled by means of the fixture shown in i. In Fig. 4 the cathode 3 shown as held in firm engagement with a base plate 55 by means of spring compressed plungers E and 57 having flange portions 58 and 59 which engage a corresponding flange portion 60 of the cathode 3 in supporting relationship in order to hold it firmly against the plate 55. The cathode 3 may be placed in this position by releasing the flange portions 58 and 59 by downward manual pressure on the plungers 56 and 51. In order to position the member I I with respect to the oathode there is provided an annular collar 6| adapted to engage flange portion l3 and the portion l2 of the member I! and having one end afiixed to the base plate 55. Thereby it fixedly positions member H with respect to cathode 3 during assembly. A pair of spring compressed plungers 62 and 63, similar to plungers 5B and 5? and having flanges 64! and 55 engage the flange portion l2 of the member H and hold the same into firm engagement with the collar 6!. It will be observed that in this position the cathode 3 and the member 1 I are precisely spaced with respect to each other. When they are thus held they may be sealed into a single unit by the introduction of the ring 2i and the sealing of the three elements together by means of heat.

It will be apparent to those skilled in the art that the foregoing provides a simplified, rugged and durable construction which may be readily assembled in quantity by inexperienced hands and which will at the same time permit a high degree of uniformity in the highly precise positioning of the respective parts without the necessity of any complicated measuring operations on the part of such non-skilled workers. Moreover, because of the novel electrode configuration it will be found that the device will be capable of handling a relatively high power output.

Whilewehav'e showd and described a-particu larembodiment 'of theinvention, it'will be obvious to those shilledintheartthat various" changes andmodifications may be'made without departing from theinvention in its broader aspects and'we,

therefore, aiminthe'appended claims to cover all-such changes and modifications asfall within the true spirit and scope of theinvention.

What'weclaim as new andd'esire to secure-by Eetters-Patentofthe United States is:

1. An electron discharge device having an anode structure" comprising a metallic cylinder and an annular anode afiixedthereto in insulating relationship with respect thereto across one end thereof; a grid structure'comprising a metalliccylin'deranda grid'of generally annular shape conductively.'supportedtherefrom across one end thereof, and a cathode structure comprising a flat metallicpjo'rtion and an annular cathode supportedtherefromin insulated relationship thereto; theinner peripheryof a-longitudinal portion of said" first mentioned cylinder fixedly engaging theouter periphery of a longitudinal portion of said secondmentionedpylinder wherebysaid an odeis'spaced in fixed relationship to said grid,

theother' end ofsaid secondmentioned cylinder being"affixed-to said fiat metallic portionwhereby said anode and said grid are spaced infixed relationship to said cathode.

2. An electron discharge device having an anode structure comprising a, metallic cylinder and an annular anode afiixed thereto in insulating relationship with respect thereto across one end thereof, a grid structure comprising a metallic cylinder and a grid of generally annular shape conductively supported therefrom across one end thereof, and a cathode structure comprising a flat annular metallic portion and an annular cathode supported therefrom in spaced insulated relationship thereto, the inner periphery of a longitudinal portion of the other end of said first mentioned cylinder fixedly engaging the outer periphery of a longitudinal portion of said end of said second mentioned cylinder whereby said anode is spaced in fixed relationship to said grid, the other end of said second mentioned cylinder being afiixed to said flat metallic portion whereby said anode and said grid are spaced in fixed relationship to said cathode.

3. An electrical discharge device comprising a metallic cylinder having an annular anode supported in insulating relationship thereto across one end thereof, a metallic grid supporting cylinder having a grid of generally annular shape supported in conductive relationship thereto across one end thereof, and a cathode supporting member having a flattened annular portion normal to the axis of said cylinders and an annular cathode supported therefrom in insulated relationship thereto, the inner periphery of a longitudinal portion of said first mentioned cylinder fixedly engaging the outer periphery of a longitudinal portion of said grid supporting cylinder whereby said anode is positioned in spaced relation to said grid, the other end of said grid supporting cylinder engaging said flattened portion whereby said anode and said grid are positioned therefrom in spaced relation to said cathode.

4. An electrical discharge device comprising a metallic cylinder having an annular anode supported in insulating relationship thereto across one end thereof, a metallic rid supporting cylinder having a grid of generally annular shape supported in conductive relationship thereto across one end thereof, and a cathode supporting member having a flattened annular portion normal'to the axis of said cylinders and an annular cathode supported therefrom in insulated relationship thereto, the inner periphery of a longitudinal portion of the other end of said first mentioned cylinder fixedly engaging the outer periphery of a longitudinal portion of said end of said grid supporting cylinder whereby said anode is positioned in spaced relation to said grid, the other end of said grid supporting cylinder engaging said flattened portion whereby said anode and said grid are positioned therefrom in spaced relation to said cathode.

5. In an electrical discharge device including an annular cathode and an annular electrode in operative relationship thereto, a structure for spacing said electrode from said cathode comprising a metallic electrode supporting cylinder having said annular electrode supported across an annular cathode and an annular electrode in operative relationship thereto, a structure for spacing said electrode from said cathode comprising a metallic electrode supporting cylinder having said annular electrode supported across one end thereof, a cathode supporting member having an annular flattened portion normal to the axis of said cylinder said annular cathode being supported centrally from said member in insulated relationship thereto and centrally of said cylinder, the other end Of said cylinder engaging said flattened portion whereby said electrode is positioned therefrom in spaced relation to said cathode in coaxial alignment therewith.

JOHN S. HICKEY. WILLIAM H. TEARE.

REFERENCES CITED The following references are of record in the one end thereof, a cathode supporting member 20 fil f this patent;

having a flattened portion normal to the axis of said cylinder, said annular cathode being supported from said member in insulated relationship thereto and centrally of said cylinder, the other end of said cylinder engaging said flattened portion whereby said electrode is positioned therefrom in spaced relation to said cathode.

6. In an electrical discharge device including UNITED STATES PATENTS 

